Electrical conductivity of M2+-doped (M = Mg, Ca, Sr, Ba) cerium pyrophosphate-based composite electrolytes for low-temperature proton conducting electrolyte fuel cells

Singh, Bhupendra; Jeon, Sang-Yun; Im, Ha‐Ni; Park, Jun-Young; Song, Sun-Ju

doi:10.1016/j.jallcom.2013.06.017

Cited by 19 publications

(30 citation statements)

References 25 publications

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“…291352 and no extra peak belonging to any crystalline phase other than tin pyrophosphate phase is visible in Sn 0.9 Si 0.1 P 2 O 7 (SSP100) and Sn 0.9 Ti 0.1 P 2 O 7 (STP100), indicating that because of the smaller ionic radius of Si 4 þ (ionic radius¼ 0.4 Å) and Ti 4 þ (ionic radius¼ 0.605 Å) than that of Sn 4 þ (ionic radius¼ 0.69 Å) [14], SiO 2 and TiO 2 are easily dissolved into tin pyrophosphate and form single phase solid solution of doped tin pyrophosphates. But the ionic radius of Ce 4 þ (ionic radius¼ 0.87 Å) being significantly larger than that of Si 4 þ [14], all the CeO 2 does not dissolve into tin pyrophosphate phase and a part of it appears as cerium pyrophosphate [10,11]. However, these peaks exactly coincide with the XRD pattern of the sample holder, indicating that the 1200 1C sintered SCP100 sample is a single phase solid solution of 0.1 mol Ce 4 þ -doped SnP 2 O 7 .…”

Section: Resultsmentioning

confidence: 99%

“…We have been working on the synthesis and characterization of cerium pyrophosphates for the application as electrolyte in low-temperature PCFCs [8][9][10]. Though the cerium pyrophosphates are thermally unstable at 4400 1C and therefore their sintering at the higher temperature is avoided [10,11], it has been observed that they give fairly dense specimens even on sintering at temperatures $ 400 1C [5,[8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…Though the cerium pyrophosphates are thermally unstable at 4400 1C and therefore their sintering at the higher temperature is avoided [10,11], it has been observed that they give fairly dense specimens even on sintering at temperatures $ 400 1C [5,[8][9][10][11]. Considering the fact that pyrophosphates of cerium and tin are generally isomorphous, with both having cubic lattice and Pa3 space group [12,13], it is expected that on partially replacing Sn 4 þ ion in SnP 2 O 7 by Ce 4 þ ion, Ce 4 þ ion would be easily incorporated into tin pyrophosphate lattice, although the ionic radius of Ce 4 þ ion (r=0.87 Å) is larger than that of Sn 4 þ ion (r=0.69 Å) [14], and improve the sinterability of tin pyrophosphate.…”

Section: Introductionmentioning

confidence: 99%

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Effect of partial substitution of Sn4+ by M4+ (M=Si, ti, and Ce) on sinterability and ionic conductivity of SnP2O7

Singh

Kim

Park

et al. 2015

Ceramics International

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of partial substitution of Sn4+ by M4+ (M=Si, ti, and Ce) on sinterability and ionic conductivity of SnP2O7

Singh

Kim

Park

et al. 2015

Ceramics International

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“…The ionic conductivity initially increases with increasing temperature and shows a maximum 12.2 mS·cm −1 at 210 • C. The conductivity decreases on further increase in temperature beyond 210 • C and thus the overall trend with temperature is similar to that shown by cerium pyrophosphates and cerium pyrophosphate based composite materials. 11,12,22,[26][27][28] Furthermore, the temperature of the CGP-PS1 composite was lowered to 110 • C and maintained overnight (pH 2 O = 0.12 atm) and then the conductivity was again measured with respect to the increase in temperature. The conductivity data are plotted in Figure 7a and in 110-150 • C range the conductivity values obtained second time are 1-2 orders of magnitude higher than those obtained during the first time measurement.…”

Section: Ionic Conductivity Of Cgp-ps Composites In Humidified Airmentioning

confidence: 99%

Fabrication of Dense Cerium Pyrophosphate-Polystyrene Composite for Application as Low-Temperature Proton-Conducting Electrolytes

Kim

Park

Lim

et al. 2015

J. Electrochem. Soc.

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The goal of this study is to improve the applicability of cerium pyrophosphates as dense electrolytes in proton-conducting ceramicelectrolyte fuel cells (PCFCs) in 100-230 • C, by using polystyrene as a pore-filler in partially sintered cerium pyrophosphate substrates. In this study an inorganic-organic composite membrane composed of Gd 3+ -doped cerium pyrophosphate (Ce 0.9 Gd 0.1 P 2 O 7 , CGP) and highly cross-linked polystyrene is prepared by polymerization of divinylbenzene monomers in partially sintered CGP substrates. The microstructure and electrochemical behavior of the CGP-polystyrene (CGP-PS) composites are characterized to understand their proton conductivity and long-term stability. The ionic conductivity measurement using electrochemical impedance spectroscopy (EIS) shows that the CGP-PS membranes have high ionic conductivity (>10 mS cm −1 ) in 110-200 • C range under humidified condition (water vapor pressure, pH 2 O = 0.04-0.16 atm); where CGP-PS1 shows maximum conductivities of 16.1 and 14.8 mS·cm −1 in pH 2 O of 0.16 and 0.12 atm, respectively, at 190 • C. The scanning electron microscopy (SEM) analysis of the as-prepared CGP-PS composites shows that they are dense and free of pores. The stability of the CGP-PS composites is analyzed after the long-term electrical conductivity measurement in humidified atmosphere.The development of new electrolytes with ionic conductivities ≥10 mS·cm −1 in intermediate temperature range of 100-500 • C has gained increased attention in research areas of the intermediate temperature fuel cells (ITFCs). Due to the lower energy of activation of protonic conduction, fuel cells based on proton conducting electrolytes has been considered as promising candidates for ITFCs. Considering the fact that tetravalent metal pyrophosphates (TMPs) have poor sintering-ability and the substrates sintered at high temperatures have poor proton-conductivity 1-3 several strategies to utilize TMPs as dense electrolytes in PCFCs including formation of inorganic-organic composite membranes by casting process have been reported. 4-10 Li et al. 8 fabricated defect-free nanofilms of amorphous Y-doped zirconium pyrophosphate by a novel approach comprising a combination of the layer-by-layer sol-gel process and annealing. Sato et al. 10 fabricated dense MO 2 -MP 2 O 7 (where M = Sn, Si, Ti and Zr) electrolyte membranes by reacting porous MO 2 substrate with phosphoric acid, where the reaction products formed into the pores act as pore fillers. However, unfortunately not much work is reported on the fabrication of dense composite electrolytes using cerium pyrophosphate. Earlier Chatzichristodoulou et al. 11 fabricated dense CeP 2 O 7 -KH 2 PO 4 composites. But, because of water solubility of KH 2 PO 4 , the composite was not stable the long-term conductivity measurements in humidified atmosphere. Recently, the strategy of in situ solidification of phosphoric acid loaded into partially sintered cerium phosphate substrate was employed to fabricate cerium pyrophosphate-based dense composite electr...

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“…Also, they have shown strong dependency of proton conductivity on the use of excess phosphorous in material synthesis. [14][15][16][22][23][24] The excess phosphorous is supposed to be present as amorphous P m O n phase in the as-synthesized material. 25 However, the fabrication of dense crystalline CeP 2 O 7 samples has been an issue, as the methods used for the preparation of dense samples involve heat-treatment at >600 • C, but cerium pyrophosphates are known to be thermally unstable at temperatures >400 • C and slowly decompose to CeO 2 , P 2 O 5 and a number of other secondary phosphates such as cerium metaphosphate (Ce 3 P 3 O 9 ), cerium orthophosphate (CePO 4 ) and cerium polyphosphates (Ce 3 (PO 4 ) 3 ).…”

mentioning

confidence: 99%

Ionic Conductivity of Gd³⁺Doped Cerium Pyrophosphate Electrolytes with Core-Shell Structure

Singh

Jeon

Kim

et al. 2014

J. Electrochem. Soc.

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In this work, 10% Gd 3+ -doped cerium pyrophosphates (CGPs) with core-shell structure are synthesized by reacting Ce 0.9 Gd 0.1 O 2 with H 3 PO 4 in a two-step solid-state slow digestion method. Use of high P/(Ce+Gd) ratio in initial reaction mixture gives a coreshell morphology composed of crystalline CGP core and amorphous phosphate (P m O n ) shell. The amorphous phosphate helps in densification of CGP pellets during sintering, without causing the appearance of any impurity. Variation of ionic conductivity of CGPs with temperature is studied in unhumidified and humidified air conditions, and is explained on the basis of microstructure, phosphate content and proton conduction mechanism. The basic dissolution of protons occurs in the crystalline pyrophosphate phase of material bulk at the oxygen vacancies formed due to the aliovalent doping of Gd 3+ and acidic dissolution of protons occurs in the amorphous phase due to the hydrolysis of P m O n groups. Ionic conductivities of CGP samples vary in 10 −3 −10 −2 range in 90-230 • C range in humidified air and maximum conductivity obtained is 2.91 × 10 −2 S cm −1 at 190 • C, pH 2 O = 0.16 atm. The pH 2 O dependence and long term response (for 450 h) of the ionic conductivity in humidified air is analyzed for potential application as electrolyte in proton-conducting ceramic electrolyte fuel cells.Materials with high proton conductivity have shown great potential in fulfilling the food and energy requirements of the everincreasing world population in a sustainable manner, by their application as electrolytes in electrochemical devices. 1-5 Proton conducting electrolyte-based fuel cells, which convert chemical energy to electrical energy cleanly and efficiently, has presented immense potential in this regard. 6-8 However, various material-related challenges have been major impediment toward the widespread commercialization of otherwise conceptually very simple fuel cells and, more often than not, these challenges arise from the choice of electrolyte, which has been the main deciding factor for various fuel cell configurations. 9,10 Among the various proton conducting electrolyte-based fuel cells types, the polymer electrolyte membrane fuel cells (PEMFCs) and proton conducting ceramic electrolyte fuel cells (PCFCs) have been widely studied for their widespread commercialization. However, these fuel cells suffer from a number of drawbacks. PEMFCs operate optimally ∼100 • C, require precious metal catalysts for electrode reactions and, because of being porous, waste fuel by chemical shortcircuit. Similarly, PCFCs operate optimally at >600 • C and its high operating temperature results in many limitations, such as higher system manufacture and maintenance costs, high performance degradation rates, slow startup and shutdown cycles. 11 Therefore, the development of new electrolytes with high conductivity in 100-600 • C range, which can lower the operating temperature of PCFCs and do away with the constraints on the operation of PEMFCs, is highly desired for fuel cells. 7,12 A...

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Electrical conductivity of M2+-doped (M = Mg, Ca, Sr, Ba) cerium pyrophosphate-based composite electrolytes for low-temperature proton conducting electrolyte fuel cells

Cited by 19 publications

References 25 publications

Effect of partial substitution of Sn4+ by M4+ (M=Si, ti, and Ce) on sinterability and ionic conductivity of SnP2O7

Effect of partial substitution of Sn4+ by M4+ (M=Si, ti, and Ce) on sinterability and ionic conductivity of SnP2O7

Fabrication of Dense Cerium Pyrophosphate-Polystyrene Composite for Application as Low-Temperature Proton-Conducting Electrolytes

Ionic Conductivity of Gd³⁺Doped Cerium Pyrophosphate Electrolytes with Core-Shell Structure

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Electrical conductivity of M2+-doped (M = Mg, Ca, Sr, Ba) cerium pyrophosphate-based composite electrolytes for low-temperature proton conducting electrolyte fuel cells

Cited by 19 publications

References 25 publications

Effect of partial substitution of Sn4+ by M4+ (M=Si, ti, and Ce) on sinterability and ionic conductivity of SnP2O7

Effect of partial substitution of Sn4+ by M4+ (M=Si, ti, and Ce) on sinterability and ionic conductivity of SnP2O7

Fabrication of Dense Cerium Pyrophosphate-Polystyrene Composite for Application as Low-Temperature Proton-Conducting Electrolytes

Ionic Conductivity of Gd3+Doped Cerium Pyrophosphate Electrolytes with Core-Shell Structure

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Ionic Conductivity of Gd³⁺Doped Cerium Pyrophosphate Electrolytes with Core-Shell Structure